The embodiments described herein relate generally to reduction of electromagnetic interference (EMI), and more specifically, to reducing conducted EMI in electronically commutated motors and switching power supplies.
At least some known electronic devices produce unwanted electrical noise. Such electrical noise can adversely affect other electronic circuit components either within the electronic device itself or in nearby external electronic devices. Conducted EMI is an electrical noise current which is typically present in the radio-wave frequency range and sometimes referred to as radio frequency interference (RFI). This current originates from within a system of electrical devices rather than from an outside source such as a radio signal transmitter. Electric power supplies of electric motors are sometimes significant generators of EMI. In connection with electric power supplies, EMI is undesirable because, for example, it can disturb the operation or degrade the performance of other equipment connected to the same source of power.
In residential and industrial applications, federal regulations have required manufacturers to control conducted EMI generated by power electronic devices. More specifically, all motor drive products in residential and commercial applications must meet a corresponding EMI standard, such as FCC Class A (commercial) and Class B (residential). Class A has a limit that is 10 dBuV higher than Class B. To reduce EMI in electric motors, at least some manufacturers connect large, bulky EMI filters to the motor controller of an electric motor, which typically require manual installation and take up significant space. However, as demand for smaller, more compact electric motors increases, manufacturers are limited in EMI filter design, size, and cost.